Sergio, I think that your circuit is really excellent demonstration of an engineering skill. I don’t know you but I am glad that you participate in this thread. I know about Keantoken a bit more and followed his fascinating progress in this forum. I am just an old retired telecommunication engineer and audio is my hobby to kip my old gray matter oiled. What I learned more then forty years ago about semiconductors now slowly is coming back and I started to use spice simulator not so long ago.
What do you think if your circuit could be made simpler whiteout loosing to much of its performance, still distortion could stay in ppm region?
Another thing to make it with high gain, let say 20 to 30 dB and then add powerful output buffer to get power amp with no GNFB. I was trying to simulate an output buffer(trying different configuratio) but never was satisfied with distortion level.
Damir

Here is new shuntreg simulation. I am trying to keep just one jfet ccs as in this case output voltage adjustment is possible with one trimer(R7 in this case). Here CCS voltige is 2.2 V and I think its on safe side of the knee(in saturation region).
dado

Thanks Damir for your kind words, I'll try to do what you ask , but the components used here are really cheap , the 20 transistors used in this circuit will cost less than a dollar. I do not really see the problem

About the power supply , have you consider The Kmultiplier from Kean, I use a very similar soluction ,It is really very low noise, and have very good stability , and is less complex than the one you are doing. But the output impedance is a bit higher.

Thanks Damir for your kind words, I'll try to do what you ask , but the components used here are really cheap , the 20 transistors used in this circuit will cost less than a dollar. I do not really see the problem

About the power supply , have you consider The Kmultiplier from Kean, I use a very similar soluction ,It is really very low noise, and have very good stability , and is less complex than the one you are doing. But the output impedance is a bit higher.

Someone said the less is better, and Einstein said " Everything should be made as simple as possible, but not simpler". OK it is question of PCB too, simpler to make.
Regarding power supply, there is oppinion that nothing can beat good shunt regulator and I need to lower power voltage to as mine transformer has 2x30V.
Damir